Array-based sensing has emerged as a potentially powerful tool for the detection of chemically diverse analytes. Based on cross-responsive sensor elements, rather than receptors for specific species, these systems may produce composite responses unique to an odorant, in a fashion similar to the mammalian olfactory system. Previous array detectors for electronic noses have employed a variety of strategies that have generally used weak chemical interactions (e.g., physical adsorption), including the use of conductive polymers and polymer composites, fluorescent dye-doped polymer systems, tin oxide sensors, and polymer coated surface acoustic wave devices. In addition, most approaches to electronic nose technology with cross-reactive sensors have poor chemical selectivity while being extremely sensitive to variations in humidity, a fatal flaw for real-world use.
In contrast to prior electronic nose platforms, two-dimensional colorimetric sensor arrays have a much greater ability to discriminate among similar analytes. A colorimetric sensor may include one or more materials that undergo a change in spectral properties upon exposure to a change in the environment of the sensor. The change in spectral properties may include a change in the absorbance, fluorescence and/or phosphorescence of electromagnetic radiation, including ultraviolet, visible and/or infrared radiation. Since stronger chemical interactions than just physisorption are utilized, the sensitivities of such arrays may be in the few ppb regime, and the arrays may be engineered to be immune to changes in humidity. Current technologies for analyzing two-dimensional colorimetric sensor arrays including flatbed scanners and high resolution cameras that require a computer for data processing.